Raman光谱拉曼光谱42左健理化中心.pptx

(surface enhanced Raman spectroscopy)SERSRaman spectroscopy:high characteristic good spatial resolution(micro Raman)minimal sample preparation all solvents can be usedbut:biological samples often show high fluorescence biological molecules appear often at low concentration levelWhy SERS spectroscopy?SERS quenches fluorescenceessential oil10 mmRamansilver colloidsM.x piperita514.5 nm200015001000500Wavenumber/cm-1Raman Intensity SERS improves the detection limit:Adenine10-8 M10-7 M10-6 M10-5 M10-3 M10-2 M10-1 M15001000500Raman IntensityRamanWavenumber/cm-115001000500Wavenumber/cm-1 Raman IntensitySERS How does SERS work?The SERS EM enhancementEOmetal colloidexcitationdetectionSERSmoleculeSERS EM enhancement shape effectSERS:Excitation of plasmon resonances in Ag(Au or Cu)nanoparticlesRaman spectroscopy utilizes optical properties of nanostructuresWavelength nmSCS nmJ.Kottmann et al.,IFH Field Theory Group,ETH ZrichAg,Au or Cu Wavelength/nmScattering Cross sectionFieldenhancementSERS:Raman spectroscopy utilizes optical properties of nanostructuresJ.Kottmann et al.,IFH Field Theory Group,ETH ZrichWavelength nmSCS nm*10SERS EM enhancement SERS EM enhancement shape effectshape effectScattering Cross sectionWavelength/nmFieldenhancementSERS:Raman spectroscopy utilizes optical properties of nanostructures20 nmJ.Kottmann et al.,IFH Field Theory Group,ETH ZrichAg,Au or Cu SERS EM enhancement SERS EM enhancement aggregation effectaggregation effectFieldenhancement4002001005020105210.50.2Scattering Cross sectionWavelength/nmTypical Typical SERS SERS media media 不同形状金纳米粒子的表面增强拉曼光谱 自组装好的不同形状的金纳米粒子的硅片浸没在20mM NaSCn 的溶液里,取出后测量其SERS信号以以SCN-作为探针分子作为探针分子,绿光绿光(51415nm)作为作为激发光波长得到的激发光波长得到的SERS谱图谱图具有较高SERS 活性的粗糙铂电极的STM(a)和镍纳米线阵列的A FM(b)图像各种过渡金属表面上吸附的吡啶在最强峰电各种过渡金属表面上吸附的吡啶在最强峰电位下的表面增强拉曼谱图位下的表面增强拉曼谱图Near-field Raman spectroscopyNear-Field MicroscopyRayleigh LimitNear-field resolutionNear-Field Geometries Schematic Near-Field Microscope Set-upL.Novotny and C.Hafner,Phys.Rev.E 50(1994).Light at Small AperturesAluminumHE11250 nm160 nmNear-field Apertures pulled etched/old etched/newTransmission:0.0001%0.1%Stckle et al.,Appl.Phys.Lett.75,161(1999)Investigation of Liquid-Liquid InterfacesNF Raman studies of water-carbon-tetrachloride interface Raman intensity of water stretching vibration vs.the distance covered by the piezo translatorNF Raman studies of water-carbon-tetrachloride interfaceRaman spectral shift of water stretching vibration vs the distance covered by the piezo translatorInvestigation of Chemical Reactions using NF-RamanHeterogeneous CatalysisHeterogenous CatalysisCorrelation of Topography and Spectra500 nmTopographyC.Fokas and V.Deckert,Appl.Spectrosc.56,192(2002)TERS-Tip Enhanced Raman SpectroscopySampleSingle SERS active particleAFM cantileverIllumination/collection opticsR.Stckle,Y.D.Suh,V.Deckert,R.Zenobi,Chem.Phys.Lett.,2000,318,131.